Terrestrial point-to-point communications links often used parabolic antennas mounted on the roof or sides of buildings. Households in residential areas typically use a parabolic antenna to receive electromagnetic waves from a broadcast satellite. Because this type of satellite dish has a beam that points out of a reflector, it must be mounted away from the house in order to tilt the dish and point it at the sky. The dish is sometimes also mounted on the roof or balcony of a house and directed at a satellite. This type of dish antenna typically comprises a reflector, feedhorn element and a converter, with the feedhorn and converter disposed on the focal position of the reflector. In heavy winds, the satellite dish can be broken. Additionally, a parabolic antenna is sometimes unsitely and spoils the aesthetic appearance of many buildings or houses.
A planar antenna can sometimes be used and placed directly on the side of the building or house to add strength to the antenna and also make its appearance more aesthetic. However, if the beam comes directly out of the surface ("on bore site"), the antenna will be directed at the building next door when mounted on a vertical surface.
Some microstrip array antennas have been designed to have a beam tilt such that a beam radiated from the antenna is deviated from a direction perpendicular to the plane of the antenna. For example, an antenna could be given a beam tilt of 23 or 27 degrees. The beam tilt can be obtained by giving phase differences to a plurality of radiating elements that constitute a phase array. An example of such antenna is disclosed in U.S. Pat. No. 5,181,042 to Kaise et al., where a planar microstrip array antenna has a beam tilt that is formed from a plurality of pairs of circularly polarized wave radiating elements.
However, the Kaise et al. patent, the disclosure which is hereby incorporated by reference in its entirety, has one fixed scan angle and the beam scan is fixed in the beamformer. No adjustment, or more importantly, selection of possible scan angles is possible.
U.S. Pat. No. 5,189,433 to Stern et al., the disclosure which is hereby incorporated by reference in its entirety, discloses a slotted microstrip electronic scan antenna where a network of striplines are mounted on an opposed surface of a dielectric substrate. A scanning circuit is connected to control terminals of circulators for selectively completing a radio frequency transmission path between an input/output stripline and coupling striplines. Each linear array is directional, having a major lobe and each major lobe is oriented in a different direction. The scanning circuit is periodically switched between the linear arrays, and causes the antenna to scan a region of space via a different major lobe. Although the beam can be scanned, the Stern et al. solution is not a simple low cost implementation, such as could be used for terrestrial point-to-point or TV receive applications where an electrical scan capability would not be required as in the Stern et al. patent.
U.S. Pat. No. 5,210,541 to Hall et al., the disclosure which is hereby incorporated by reference in its entirety, discloses a patch antenna array having multiple beam-forming capability using a feed network on a microstrip substrate with patches overlaying an upper substrate. Linear series-connected patch arrays are each resonant and may have open circuits at each end. A traveling wave arrangement of feed lines is provided, and in one embodiment, the total number of beams can be generated as twice the number of feed lines. Again, a simplified selectable structure to scan the beam to a desired location such that a user can obtain a desired and scanned beam at a predetermined location is not disclosed.